The research proposed in this application is designed to study late stages of tumor progression, especially invasion and metastasis of chemically-induced skin tumors. In this context we intend to study the evolution of markers of malignant conversion that proved useful to predict the early behavior of tumors, (changes in GGT, keratin polypeptide and chromosomal alterations) in invasive and metastasizing tumors produced by different protocols of chemical carcinogenesis. In addition to these parameters we will also investigate changes in cell surface alterations that have been linked to the "advanced carcinoma phenotype" i.e., binding to laminin, fibronectin collagen IV, and lectins. Furthermore we will probe the biological behavior of tumors by studying their invasive and colonizing abilities. The picture of the invasive- metastasizing phenotype will e completed by correlating these changes with a histopathological and cytogenetical evaluation of the tumors, as well as by a study of eventual oncogene activation. During these planned experiments we propose to prove that the three stage carcinogenesis is more effective in producing invasive and metastasizing tumors than two stage carcinogenesis protocols. In particular we are interested in proving that radicals play an important role in the production of the advanced carcinoma phenotype. A series of experiments using benzoyl peroxide and hydrogen peroxide as third stage agents are proposed to further investigate this topic. Additional experiments using modifiers of free radicals are presented as an approach for a better understanding of the mechanisms by which free radical- generating compounds enhance the aggressive behavior of skin tumors. Our proposal contains experiments to investigate not only eventual differences in the tumor-metastasis yields with different protocols of chemical carcinogenesis; we also propose to study differences in the biological behavior and in some essential characteristics of advanced neoplasia, that have been shown to be important components of the "invasive-metastasizing" phenotype. This will result in a more complete picture of experimental skin tumor development which has been extremely well studied in its initial stages but whose later stages (evolution of carcinomas, invasion, and metastasis) have not been studied in depth in this model of chemical carcinogenesis.